1. Field of the Invention
This invention relates in general to hydraulic torque wrenches and more particularly to ratcheting hydraulic torque wrenches.
2. Description of the Prior Art
The petro-chemical industry, as well as industry in general, relies on extensive use of pipes and large valves with bolted or studded flanges. Very large make-up torque of the magnitude of 2,500-5,000 ft-lbs rising to as high as 75,000 ft-lbs are needed to tighten down the nuts on these flanges. Additionally, break-out torque required may be four or five times the corresponding make-up torque needed for a given flange.
Consequently, heavy-duty wrenches, primarily hydraulic torque wrenches, are needed. Wrenches in the prior art use a relatively complex system of gears, bushings, drive pawls, pins, etc., resulting in wrenches which are physically large, heavy and particularly cumbersome. This complexity gives rise to equipment mechanical failure.
Wrenches in the prior art have a poor mechanical advantage with the result that their torquing capacity is small in comparison to their bulk. The more advanced wrenches in the prior art require reaction plates to operate. Some, because of their pinned wrench bodies, often require reaction rollers to increase the mechanical advantage of the wrench. These wrenches usually are not consistently accurate within many required specifications. While high torque is developed by these designs for a given weight of the wrench, a great amount of space is still required around the workpiece for such wrenches to operate. Space restrictions exist between flange nuts and pipe walls or surfaces adjacent to the flange. This problem of turning a bolt or nut in a confined space is no small problem and has been an unsolved need in industry.
Safety is a large factor not only from the obvious awkwardness of handling a large, heavy wrench (approximately 80 lbs) leading to the malalignment of a wrench on a bolt or dropping a wrench in an unbalanced position, but also for the improper tightening of a nut itself. In one example, improper tightening of compressor valves can result in a lethal explosion and fire when natural gas escapes after the nuts on studs are over-tightened and fail from stress fatigue and tension.
Examples of the present state of the art can be seen in the following U.S. Pat. Nos.:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED TITLE ______________________________________ 3,745,858 John L. Biach 7/17/73 TORQUING DEVICE 4,027,561 John K. Junkers 6/07/77 HYDRAULIC WRENCH 4,385,533 Bobby W. Collins 5/31/83 UNIVERSAL REACTION PLATE 4,448,096 Bobby W. Collins 5/15/84 FLUTTER LIFT FOR TORQUE WRENCH ______________________________________